Summer 2019-21 True Natural Health Magazine – Your Questions Answered
By Roger French


QUESTION: I have mild osteoarthritis at the bases of both thumbs – and as I have used my hands a lot, this could be a factor. I eat a lot of tomato, which I know can aggravate arthritis due to the solanine content.

Would the solanine content be minimised if I select only tomatoes that are very ripe? In other words, does the solanine content decrease with the ripening of the fruit?




The short answer is that solanine is at its highest levels in green tomatoes – as it is in green potatoes – and decreases to its minimum levels in dead ripe fruit. So, yes, your best chance of avoiding irritation from solanine is to consume only perfectly-ripe tomatoes.

Tomatoes are low in calories, and contain useful levels of potassium, vitamin C and carotenoids, especially the carotenoid, lycopene, which is strongly protective against prostate cancer and no doubt other cancers as well. Lycopene is responsible for the red colour of tomatoes, so the redder the better.

They are the most popular vegetable grown in home gardens because the plants are easy to grow and produce an abundance of fruit.

Most plants contain natural pesticides, and solanine is the one in tomatoes. This toxic compound is present in all members of the nightshade family, which includes tomatoes, capsicum, potatoes, eggplant and chilies.

Solanine is a glycol-alkaloid compound and is present in all parts of the plant. It is a bitter tasting and toxic even in small concentrations.

In potatoes, the parts which have turned green have the highest levels of solanine, which are much greater and more harmful than the solanine in tomatoes. When potatoes are green, they should not be eaten.

In tomatoes, the highest level of the solanine group of chemicals, called tomatine, occurs when they are immature and green. The concentration can be up to 500 mg per 1 kg of fruit, according to the website As the tomato ripens, the tomatine decreases rapidly to levels less than 5 mg per kg in fully ripe tomatoes. These low levels usually pose no health problems for humans.

But for cats, even the solanine in ripe tomatoes is harmful.

In most cases, tomatoes ripened on the bush have lower levels of solanine than greenhouse tomatoes because the latter have often been harvested green.

The softer and sweeter the ripe tomato, the less solanine it contains.

 Potatoes naturally produce solanine and chaconine, a related glycol-alkaloid, as a defence against pests.

When potato tubers are exposed to light, they turn green and increase glycol-alkaloid production as a natural defence against the uncovered tuber from being eaten. The green colour is chlorophyll, which is harmless, but is an indication of a high solanine level.  A bitter taste is another indicator of toxicity.

Higher solanine can also result from damage during harvesting or transport. Cooking does not destroy solanine.

Some varieties of potatoes contain higher levels of solanine than others. Newer varieties contain much less than older varieties.


Symptoms. The first symptoms of toxicity – dizziness and shortness of breath (dyspnoea) – start at a dose of around 200 mg, which would require the consumption of a lot of green tomatoes. Later symptoms in the gut could be diarrhoea, stomach cramps, nausea, vomiting and burning of the throat. Nerve symptoms can be dizziness, headaches and irregular heartbeat (dysrhythmia). Children and adults with tomato allergies and sensitivity are the most affected by the solanine in green tomatoes.

In potatoes, the concentrations of glycol-alkaloids are 3 to 10 times greater in the peel than in the flesh and they are higher in potatoes that have sprouted.

How many potatoes might make you sick (or die)? Estimates are around 2 – 2.5 kg of normal potatoes or 1 kg of green potatoes. A large potato weighs roughly a quarter kg, so it’s reasonable to expect that some people could get sick from eating eight potatoes or four green ones – which is a lot of potatoes.

Accordingly, poisoning from potatoes is rare and even more rare from tomatoes. The well known natural therapist, Andrew Weil, points out that there hasn’t been a single case of solanine poisoning in the US from potatoes in the last 50 years. This was reported by Science-Based Medicine,

Finally, for the technically minded, the botanical names for the main members of the nightshade family, genus Solanum, are the potato (Solanum tuberosum), the tomato (Solanum lycopersicum) and the eggplant (Solanum melongena).